1. Field of the Invention
This invention relates to signal processing apparatuses and, more particularly, to a signal processing apparatus used to process a composite video signal outputted from, for example, a time lapse VCR wherein the composite video signal contains predetermined information and video components respectively provided in first and second predetermined positions of a field.
Meanwhile, the invention is concerned with a signal processing apparatus which processes a signal reproduced from a magnetic tape and having a video component and predetermined information component.
2. Description of the Related Art
According to a conventional monitor camera system shown in FIG. 16, a plurality of monitor cameras 1a-1d output respective video signals Va-Vd. The video signals Va-Vd are thinned out every field by a multiplexer 4. The thinned-out video signals are intermittently recorded onto a video cassette 3 by a time lapse VCR 2. On a video tape 3a, video tracks Va-Vd are formed, for example, as shown in FIG. 17. The video tracks Va-Vd are recorded with ID signals corresponding to the monitor cameras 1a-1d. To conduct reproduction from the video cassette 3 containing intermittent recordings, it is a practice to add pseudo vertical sync signals to the respective reproduced video signals Va-Vd by using the time lapse VCR 2 for the purpose of preventing the missing of a vertical sync signal or erroneous detection of vertical sync signal due to switching noise. Meanwhile, the reproduced video signals change in kind every field. Accordingly, the reproduced video signals Va-Vd are written onto memories 4a-4d in accordance with their ID signals by the multiplexer 4, which are thereafter outputted therefrom onto the monitor 5. As a result, reproduced videos Va-Vd are divisionally displayed on the monitor 5 as shown in FIG. 18.
However, when the video signals Va-Vd are written to the memories 4a-4d by the multiplexer 4, the timing of write start is determined based on the pseudo vertical sync signal. As a result of this, if the pseudo vertical sync signal is inaccurate in position of adding, deviation may occur at a start of writing. This results in vertical deflection in the reproduced videos Va-Vd being displayed on the monitor 5. That is, the video component starts at 30 H in each field. Nevertheless, if the pseudo vertical sync signal is deviated in adding position as shown in FIG. 19, a deviation occurs in the reproduced video displayed on the monitor 5.
On the other hand, if the I) signal be not successfully reproduced, the multiplexer 4 possibly writes a reproduced video signal into an incorrect memory or outputs onto the monitor 5 an input from the time lapse VCR 2 without processing. In either case, it is difficult for the reproduced videos Va-Vd to properly display on the monitor 5.
It is, therefore, a primary object of the present invention to provide a video signal processing circuit which is capable of preventing deflection in reproduced videos.
Another object of the invention is to provide a video signal processing circuit which can improve the accuracy of determining a predetermined information component contained in a reproduced signal.
According to the present invention, a signal processing apparatus for processing a video signal having predetermined information component provided in a first predetermined position in each field, comprises: a detector for detecting the predetermined information component; a processor for specifying a second predetermined position of the video signal based on the predetermined information component detected; a memory; a write controller for writing the video signal from the second predetermined position to the memory; and a read controller for reading out the video signal written in the memory.
Detected is a predetermined information component provided in a first predetermined position of each field by the detector. The processor specifies a second predetermined position of a video signal based on a detected predetermined information component. The write controller writes the video signal from the second predetermined position to the memory. The read controller reads the video signal thus written out of the memory. As a result of this, there is no vertical deflection in a video signal read from the memory.
In one aspect of the invention, in the processor a particular information detecting circuit detects particular information from the predetermined information component. A first counter counts the number of lines based on a detection time point, as a reference, of the particular information and outputs second predetermined position information.
In one embodiment, the predetermined information component lies over a plurality of lines. The specifying means includes a start position detecting circuit to detect a start position of the predetermined information component. A second counter counts the number of lines based on a detection time point, as a reference, of the start position and outputs the second predetermined position information.
Further, an end position detecting circuit detects an end position of the predetermined information component. A third counter counts the number of lines based on a detection time point, as a reference, of the end position and outputs the second predetermined position information.
If a plurality of second position information are obtained in this manner, a selector selects any second predetermined position information according to a predetermined order.
The write controller resets a write address according to the second predetermined position information outputted from the select means.
Incidentally, the second predetermined position is a start position of an effective component of the video signal.
According to the present invention, a signal processing apparatus for processing a video signal having a predetermined information component provided in a first predetermined position of each field, comprises: a detector for detecting the predetermined information component; and a signal generator for outputting a tracking control signal based on a reproduction characteristic.
The magnetic tape is recorded with a signal including a video component and a predetermined information component. The detector detects a reproduction characteristic of a portion including a predetermined information component, based on a reproduced signal from the magnetic tape. On the other hand, the signal generator outputs a tracking control signal based on a detected reproduction characteristic. Consequently, it is possible to accurately determine a predetermined information component.
In one aspect of the present invention, the magnetic tape is formed with a plurality of tracks, and the video component and the predetermined information component is reproduced from each track. Here, the plurality of tracks are formed in a helical scan scheme on the magnetic tape. In the detector, detected is a reproduction characteristic of a portion including a predetermined information component, as follows. First, a missing detecting circuit detects a missing portion of a reproduced signal. An enable circuit enables an output of the missing detecting circuit in a predetermined position of each track. The signal generator outputs a tracking control signal in response to an output of the missing detecting circuit being enabled.
In another aspect of the present invention, the detector detects a reproduction characteristic, as follows. That is, first a component detecting circuit detects the predetermined information component, and then a determination circuit determines a content of the predetermined information component. The signal generator outputs a tracking control signal in response to a result of determination of the determining means.
In another aspect of the present invention, an eliminator removes a predetermined frequency component from the reproduced signal, and a characteristic controller changes a frequency characteristic of the eliminator depending upon a reproduction position. Here, the eliminator includes a plurality of filters different in cut-off frequency, and the characteristic controller selects any one of the plurality of filters. That is, the characteristic controller lowers a cut-off frequency when reproducing the predetermined information component. The cut-off frequency at a time of reproduction of the predetermined information component is included in a frequency band of the video component.
The above described objects and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.